Naruto’s final compiled volume to have a secret in its wrap-around jacket

Naruto‘s final chapter may have put the beloved manga series to a close, but for its 72nd and final compiled volume, or Tankoubon, there will be a “Secret” going to be revealed in its wrap-around jacket

What will this secret be? We will never know until February 4, 2015, which is when the final volume will be released in Japan.

So what do you think is this big secret?